    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *     http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.configuration2.resolver;
    018
    019import java.io.IOException;
    020import java.io.InputStream;
    021import java.net.URL;
    022import java.net.URLConnection;
    023import java.util.HashMap;
    024import java.util.Map;
    025
    026import org.xml.sax.EntityResolver;
    027import org.xml.sax.InputSource;
    028import org.xml.sax.SAXException;
    029
    030/**
    031 * The DefaultEntityResolver used by XML Configurations.
    032 * @author <a
    033 * href="http://commons.apache.org/configuration/team-list.html">Commons
    034 * Configuration team</a>
    035 * @since 1.7
    036 * @version $Id: DefaultEntityResolver.java 1842194 2018-09-27 22:24:23Z ggregory $
    037 */
    038public class DefaultEntityResolver implements EntityResolver, EntityRegistry
    039{
    040    /** Stores a map with the registered public IDs.*/
    041    private final Map<String, URL> registeredEntities = new HashMap<>();
    042
    043    /**
    044     * <p>
    045     * Registers the specified URL for the specified public identifier.
    046     * </p>
    047     * <p>
    048     * This implementation maps {@code PUBLICID}'s to URLs (from which
    049     * the resource will be loaded). A common use case for this method is to
    050     * register local URLs (possibly computed at runtime by a class loader) for
    051     * DTDs and Schemas. This allows the performance advantage of using a local
    052     * version without having to ensure every {@code SYSTEM} URI on every
    053     * processed XML document is local. This implementation provides only basic
    054     * functionality. If more sophisticated features are required, either calling
    055     * {@code XMLConfiguration.setDocumentBuilder(DocumentBuilder)} to set a custom
    056     * {@code DocumentBuilder} (which also can be initialized with a
    057     * custom {@code EntityResolver}) or creating a custom entity resolver
    058     * and registering it with the XMLConfiguration is recommended.
    059     * </p>
    060     *
    061     * @param publicId Public identifier of the Entity to be resolved
    062     * @param entityURL The URL to use for reading this Entity
    063     * @throws IllegalArgumentException if the public ID is undefined
    064     */
    065    @Override
    066    public void registerEntityId(final String publicId, final URL entityURL)
    067    {
    068        if (publicId == null)
    069        {
    070            throw new IllegalArgumentException("Public ID must not be null!");
    071        }
    072        getRegisteredEntities().put(publicId, entityURL);
    073    }
    074
    075    /**
    076     * Resolves the requested external entity. This is the default
    077     * implementation of the {@code EntityResolver} interface. It checks
    078     * the passed in public ID against the registered entity IDs and uses a
    079     * local URL if possible.
    080     *
    081     * @param publicId the public identifier of the entity being referenced
    082     * @param systemId the system identifier of the entity being referenced
    083     * @return an input source for the specified entity
    084     * @throws org.xml.sax.SAXException if a parsing exception occurs
    085     */
    086    @Override
    087    public InputSource resolveEntity(final String publicId, final String systemId)
    088            throws SAXException
    089    {
    090        // Has this system identifier been registered?
    091        URL entityURL = null;
    092        if (publicId != null)
    093        {
    094            entityURL = getRegisteredEntities().get(publicId);
    095        }
    096
    097        if (entityURL != null)
    098        {
    099            // Obtain an InputSource for this URL. This code is based on the
    100            // createInputSourceFromURL() method of Commons Digester.
    101            try
    102            {
    103                final URLConnection connection = entityURL.openConnection();
    104                connection.setUseCaches(false);
    105                final InputStream stream = connection.getInputStream();
    106                final InputSource source = new InputSource(stream);
    107                source.setSystemId(entityURL.toExternalForm());
    108                return source;
    109            }
    110            catch (final IOException e)
    111            {
    112                throw new SAXException(e);
    113            }
    114        }
    115        // default processing behavior
    116        return null;
    117    }
    118
    119    /**
    120     * Returns a map with the entity IDs that have been registered using the
    121     * {@code registerEntityId()} method.
    122     *
    123     * @return a map with the registered entity IDs
    124     */
    125    @Override
    126    public Map<String, URL> getRegisteredEntities()
    127    {
    128        return registeredEntities;
    129    }
    130}